This invention relates to a system and method for removing liquid from a rear window (i.e., backlite) of a vehicle such as a car, truck, or sport utility vehicle. More particularly, the system and/or method may include a rear spoiler or air deflector designed to accelerate air/wind flow and direct the same toward the backlite which may include a hydrophobic coating provided thereon, so that liquid (e.g., rain) and/or dirt may be easily removed from the backlite.
Conventionally, rain and dirt are typically removed from vehicle backlites (i.e., rear windows) using a rear wiper(s), especially in sport utility vehicles. Unfortunately, rear wipers tend to be rather fragile, costly and prone to damage.
In view of the above, it is apparent that there exists a need in the art for a system and corresponding method for removing rain and/or dirt from vehicle backlites without the need for use of a rear wiper.
Rear spoilers for directing air/wind onto vehicle backlites are known in the art. For example, see U.S. Pat. Nos. 4,674,788, 4,881,772 and 5,845,960, the disclosures of which are hereby incorporated herein by reference. The ""788 patent discloses a rear spoiler which may be manipulated between two different positions. FIG. 1 is a perspective view of vehicle 3 including the ""788 rear spoiler 5 mounted thereon. In the first position, spoiler 5 diverts air flowing along upper vehicle body surface 7 (i.e., roof) upwardly so as to exert a downward force and enhance traction of vehicular wheels 9. In the second position, spoiler 5 guides air flow toward a rear window (i.e., backlite) 11 surface so as to remove rain water, dust and so forth from the major exterior surface thereof.
Unfortunately, the system of the ""788 patent is less than desirable for at least the following reasons. First, while the spoiler may guide air flow toward the backlite, it does not serve to accelerate the speed of the air flow. Thus, when the vehicle is traveling at rather slow speeds (e.g., 20 mph), the air flow will often be insufficient to clean/remove rain and the like from the surface of backlite 11. Second, the backlite appears to be of conventional glass in the ""788 patent (the contact angle xcex8 of conventional uncoated soda lime silica glass is about 22-24 degrees). As a result, even when air is caused to flow across the surface of the backlite, rain may not be sufficiently removed therefrom due to the inherent tendency of glass to hold water on its surface due to its naturally low contact angle xcex8.
The ""772 and ""960 patents also disclose rear spoilers designed to direct air flow toward backlites. Unfortunately, the ""772 and ""960 patents suffer from the same problem as the ""788 patent in that the backlite appears to be of conventional glass thus having an inherently low contact angle xcex8. As a result, even when air is caused to flow across the surface of the backlite, rain may not be sufficiently removed therefrom due to the natural tendency of glass to hold water on its surface due to its inherently low contact angle xcex8.
It will be apparent from the above that there exists a need in the art for a system and/or method for efficiently removing water (e.g., rain) from the exterior surface of a rear backlite.
It is a purpose of different embodiments of this invention to fulfill any or all of the above described needs in the art, and/or other needs which will become apparent to the skilled artisan once given the following disclosure.
An object of this invention is to provide a system and/or method for efficiently removing liquid such as rain from an exterior surface of a vehicle backlite (i.e., rear window).
Another object of this invention is to reduce the need for a rear wiper on a vehicle by providing a system and/or method which may remove a significant amount of liquid such as rain from the backlite without the need for a wiper.
Another object of this invention is to provide a rear spoiler including a plurality of venturi-like channels or passages therein for accelerating air flow and directing the accelerated air flow toward a surface of the backlite.
Another object of this invention is to provide a hydrophobic coating on the exterior major surface of a vehicle backlite so as to enable air flowing over the surface to more easily remove (or blow off) liquid such as rain therefrom.
Yet another object of this invention is to provide a hydrophobic coating on a vehicle backlite to be used in combination with a spoiler designed to accelerate air flow and/or direct the same toward the backlite with hydrophobic coating thereon, in order to efficiently remove liquid such as rain from the coated surface of the backlite. This may eliminate the need for a rear wiper in certain embodiments, and in other embodiments where a rear wiper is provided on the vehicle may reduce the need for its use to remove rain and/or dirt from the backlite""s exterior major surface.
Another object of this invention is to provide the backlite with a hydrophobic coating including sp3 carbon-carbon bonds and a wettability W with regard to water of less than or equal to about 23 mN/m, more preferably less than or equal to about 21 mN/m, and most preferably less than or equal to about 20 mN/m, and in most preferred embodiments less than or equal to about 19 mN/meter (these units may also be explained or measured in Joules per unit area (mJ/m2)).
Another object of this invention is to provide the backlite with a hydrophobic coating including sp3 carbon-carbon bonds and a surface energy C of less than or equal to about 20.2 mN/m, more preferably less than or equal to about 19.5 mN/m, and most preferably less than or equal to about 18 mN/m.
Another object of this invention is to provide the backlite with a hydrophobic coating thereon, the backlite with coating having an initial (i.e. prior to being exposed to environmental tests, rubbing tests, acid tests, UV tests, or the like) water contact angle xcex8 of at least about 70 degrees, more preferably of at least about 100 degrees, even more preferably of at least about 110 degrees, and most preferably of at least about 125 degrees.
Another object of this invention is to provide a hydrophobic coating for a vehicle backlite, wherein at least about 15% (more preferably at least about 25%, and most preferably at least about 30%) of the bonds in the coating are sp3 carbon-carbon (Cxe2x80x94C) bonds; and wherein the coating includes by atomic percentage at least about 5% silicon (Si) atoms (more preferably at least about 15%, and most preferably at least about 20% Si), at least about 5% oxygen (O) atoms (more preferably at least about 15% and most preferably at least about 20%), at least about 5% hydrogen (H) atoms (more preferably at least about 10% and most preferably at least about 15%) taking into consideration either the coating""s entire thickness or only a thin layer portion thereof. In certain embodiments, an increased percentage of H atoms may be provided near the coating""s outermost surface. In certain embodiments, the coating has approximately the same amounts of C and Si atoms.
Another object of this invention is to provide a coating for a vehicle backlite, wherein the coating includes a greater number of sp3 carbon-carbon (Cxe2x80x94C) bonds than sp2 carbon-carbon (Cxe2x80x94C) bonds. In certain of these embodiments, the coating need not include any sp2 carbon-carbon (Cxe2x80x94C) bonds.
Another object of this invention is to provide a diamond-like carbon (DLC) coating on the major exterior surface of a vehicle backlite, wherein the coating includes different portions or layers with different densities and different sp3 carbon-carbon bond percentages. The ratio of sp3 to sp2 carbon-carbon bonds may be different in different layers or portions of the coating. Such a coating with varying compositions therein may be continuously formed by varying the ion energy used in the deposition process so that stresses in the coating are reduced in the interfacial portion/layer of the DLC coating immediately adjacent the underlying substrate. Thus, a DLC coating may have therein an interfacial layer with a given density and sp3 carbon-carbon bond percentage, and another layer portion proximate a mid-section of the coating having a higher density of sp3 carbon-carbon (Cxe2x80x94C) bonds. The outermost layer portion at the surface of the coating may be doped (e.g. addition of Si, O and/or F) so that this surface portion of the coating is less dense which increases contact angle and decreases the dispersive component of surface energy so as to improve hydrophobic characteristics of the coating.
Still another object of this invention is to fulfill any or all of the above-listed objects and/or needs.
Generally speaking, this invention fulfills any or all of the above described needs or objects by providing a method of blowing water off of a rear window of a vehicle, the method comprising the steps of:
providing a vehicle including the rear window and an air deflector mounted at an elevation above at least a portion of the rear window, an exterior surface of the rear window having a contact angle xcex8 of at least about 70 degrees;
the air deflector redirecting air flow flowing over an upper surface of the vehicle and causing the redirected air flow to flow toward the rear window at an increased rate; and
the redirected air flow flowing across an exterior surface of the rear window having a contact angle of at least about 70 degrees so as to remove water from the surface of the rear window.
This invention further fulfills any of all of the above listed needs and/or objects by providing a system for enabling rain water to be removed from a major exterior surface of a backlite (i.e., rear window) of a vehicle, the system comprising:
an air deflector for redirecting air from flowing in a first direction across a surface of the vehicle to a second direction in which air flows downwardly toward the backlite, and for causing at least a portion of the air flowing the second direction to flow faster than air in the first direction; and
wherein said backlite includes a substrate with a hydrophobic coating thereon, so that the major exterior surface of the backlite has an initial contact angle xcex8 of at least about 70 degrees.
This invention will now be described with respect to certain embodiments thereof, along with reference to the accompanying illustrations.